The nfdump tools collect and process netflow data (v5, v7 and v9)
on the command line. They are part of the NfSen project.

nfcapd - netflow capture daemon.  Reads the netflow data from the
network and stores the data into files. Automatically rotate files
every n minutes (typically every 5 minutes). nfcapd reads netflow v5,
v7 and v9 flows transparently. You need one nfcapd process for each
netflow stream.

nfdump - netflow dump.  Reads the netflow data from the files stored
by nfcapd. Its syntax is similar to tcpdump. If you like tcpdump
you will like nfdump. Displays netflow data and can create lots of
top N statistics of flows IP addresses, ports etc in whichever
order you like.

nfreplay - netflow replay.  Reads the netflow data from the files
stored by nfcapd and sends it over the network to another host.

A web front-end, NfSen, is available at http://nfsen.sourceforge.net/
